Primal Quest, the multi-day suffer fest adventure race filled up in less than 12 hours. That's not quite the 10 minutes of the Pikes Peak Ascent, but bear in mind, the race costs $12,500 with a deposit of $2,500 required with application. And the racers don't even know where the race is. It's "somewhere in the Rockies."
Ouch. Writing a check like that could get you used to the pain of the race.